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LISP & VXLAN Questions

March 16th, 2020 in ENCOR 350-401 Go to comments

If you are not sure about VXLAN, please read our VXLAN tutorial.

Question 1

Explanation

An Egress Tunnel Router (ETR) connects a site to the LISP-capable part of a core network (such as the Internet), publishes EID-to-RLOC mappings for the site, responds to Map-Request messages, and decapsulates and delivers LISP-encapsulated user data to end systems at the site.

Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_lisp/configuration/xe-3s/irl-xe-3s-book/irl-overview.html

Question 2

Explanation

Proxy ingress tunnel router (PITR): A PITR is an infrastructure LISP network entity that receives packets from non-LISP sites and encapsulates the packets to LISP sites or natively forwards them to non-LISP sites.

Reference: https://www.ciscopress.com/articles/article.asp?p=2992605

Note: The proxy egress tunnel router (PETR) allows the communication from the LISP sites to the non-LISP sites. The PETR receives LISP encapsulated traffic from ITR.

Question 3

Explanation

Locator ID Separation Protocol (LISP) is a network architecture and protocol that implements the use of two namespaces instead of a single IP address:
+ Endpoint identifiers (EIDs)—assigned to end hosts.
+ Routing locators (RLOCs)—assigned to devices (primarily routers) that make up the global routing system.

Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_lisp/configuration/xe-3s/irl-xe-3s-book/irl-overview.html

Question 4

Explanation

Locator ID Separation Protocol (LISP) is a network architecture and protocol that implements the use of two namespaces instead of a single IP address:
+ Endpoint identifiers (EIDs) – assigned to end hosts.
+ Routing locators (RLOCs) – assigned to devices (primarily routers) that make up the global routing system.

Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_lisp/configuration/xe-3s/irl-xe-3s-book/irl-overview.html

Question 5

Explanation

802.1Q VLAN identifier space is only 12 bits. The VXLAN identifier space is 24 bits. This doubling in size allows the VXLAN ID space to support 16 million Layer 2 segments -> Answer B is not correct.

VXLAN is a MAC-in-UDP encapsulation method that is used in order to extend a Layer 2 or Layer 3 overlay network over a Layer 3 infrastructure that already exists.

Reference: https://www.cisco.com/c/en/us/support/docs/lan-switching/vlan/212682-virtual-extensible-lan-and-ethernet-virt.html

Comments
  1. Anonymous
    May 29th, 2020

    No Premium Member: You can test your knowledge with these questions first via this link (via Flash) or this link (via HTML). To test for this section!

  2. Micky
    July 7th, 2020

    I Think D (MAP RESOLVER) is a better answer. The cloud facing interface on R1 and R2 all other router in the cloud are considered RLOC by definition. MR respond with the mapping that leads ITR (R1) to forward traffic to ETR (R2).

  3. !nk
    July 10th, 2020

    According to RFC 6833, The LISP Mapping Service defines two new types of LISP-speaking
    devices: the Map-Resolver, which accepts Map-Requests from an Ingress
    Tunnel Router (ITR) and “resolves” the EID-to-RLOC mapping using a
    mapping database; and the Map-Server, which learns authoritative
    EID-to-RLOC mappings from an Egress Tunnel Router (ETR) and publishes
    them in a database.
    The answer should be MapServer(B).

  4. !nk
    July 10th, 2020

    Okay, after further reading the answer is A. The Map Server responds with the mappings on behalf of the ETR b/c a ‘proxy map reply flag’ is set. By default, the ETR sends(publishes) the EID-to-RLOC mappings to ITR. See “LISP Data Path” in ENCOR350-401 Official Cert Guide(p470).

  5. GZ
    July 22nd, 2020

    Q2:
    Non-LISP site <——— PETR PITR ———-> LISP site

  6. GZ
    July 22nd, 2020

    ITR means ingress (going inside LISP network)
    Proxy is used when communication between Non-LISP and LISP sites
    Non-LISP site ——-> PITR ——–> LISP site

  7. Anonymous
    November 15th, 2020

    @digitaltut what is the correct answer in Q1? Here it says A but in flash is B?

  8. digitaltutq
    November 15th, 2020

    @Anonymous: The correct answer is A. ETR.

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